Isomerization process



May 7, 1946- N. F. MYERS ISOMERZATION PROCESS Filed Jan. l1, 1944 .mb NN. b

72cm/QZ E myers nnwear JMWMGi-yorneq particularly true wheg'seflarge quantities fins are found in such feed stocks 'bj feasible to utilize such a renery cutiff .uff/and remove thesame as sludge Patented May` 7, i946 IsoMnmzATroN rno'oass No1-val F. Myers,` short mns, N. J., minor to Standard Oil Develo poration of Delaware pment Company, a cor- Application January 1l, 1944, Serial No. 517,815 y 12 Claims. (Cl. Z50-683.5) This application isa continuation-impart of copending application Serial No. 422,820, filed December 13, 1941.

The present invention relates to a process for the lcatalytic isomerization of paraillnic hydrocarbons. In particular, it relates to the catalytic isomerization of normal parafdnic hydrocarbons having atleast four carbon atoms in the molecule wherein feed stocks predominating in these types of hydrocarbons are subjected to the action of Friedel-Crafts type catalysts, in the presence of halogen-containing promoters under suitable isomerization reaction conditions to produce the corresponding branched chain paraflinic hydrocarbons.

The straight chain parafllns of at least fourcarbon atoms per molecule have been isomerized in the presence of Friedel-Crafts type catalysts" and halogen-containing promoters to produce branched chain paralllns. However, numerous efforts have been made to increase the efficiency of the catalyst employed to'minimize the degradation of the feed stock lwhile in contact with that catalyst and to obtain the highest possible yields of the desired isoparaiiins consistent with the minimizing of catalyst and ractant degradation. Particularly in petroleum tities of light hydrocarbon mixtures are available but because of the fact that these mixtures oftentimes are contaminated with impurities. by reason of the particular sourceof the crude oil from which they are derived or ceding refinery operation from which they are produced, they are not particularly suitable foreconomic utilization in normal parafiln isomerization processes. Numerous methods lhave been proposed, for example, for the removal of olefins from refinery C4 cuts, said cuts being otherwise suitable for subjecting to isomerization. Thus, for example, the alkylation of the oleflnicl content of a. refinery C4- cut has sproved feasible. This is t is hardly only small amounts of olefins are present therein. In such cases, resort hasl been made in the past to pre-A treating the feed stock to an isomerlzation ref A refineries large quanby reason of some prcother processes are known. Likewise, it has been found desirable to remove sulfur and sulfur-cony taining compounds from the feed stocks. The sulfur and sulfur-containing impurities are present in the feed stocks by reason of the crude from which the hydrocarbons are derived or by reason of some previous'treating operation in the refinery. It has been found that these sulfur bodies are likewise deleterious to the most emcient utilization of the Friedel-Crafts type catalysts and should be removed from the feed stocks 'prior to contacting the same under visomerization conditions with the heretofore-mentioned'catalysts.

It is an object of the present invention to pro-A vide animproved practical and economical process for the catalytic isomerization oi.' normal paraflins of .at least four carbon atoms per molecule of ole action .zone employing a Friedel-Crafts type cat alyst with spent or partially spent aluminum 'chloride' to polymerize the oleflnic content thereo liquid. y various concentrations have been resorted to, to remove 'traces of oleflns and-'of water from normal paraffin isomeriaztion feed stocks. Various or hydrocarbon Also, pretreatments with sulfuric acid of to the corresponding isoparafflns. In particular, it is an object of the invention to avoid in so far as possible excessive catalyst degradation in such reactions due to impurtities and poisons contained in the feed stocks employed. It is a further object of the invention to provide an improved method for the isomerization of hydrocarbonl mixtures predominating essentially in normal paramns of at least four carbon atoms per molecule, said mixtures primarily originating in petroleum refinery operations' and containing small mounts of oleiins, moisture and/or sulfur bodies, said bodies having been found to be deleterious to eillcient and economical use of the Friedel-Crafts type catalysts. Otherobjects will be apparent vupon a' fuller understanding of the invention to be more fully hereinafter described.

VIt has now been foundexpedient in carrying out a commercial operation of this type, particularly where ordinary refinery C4 and/or Cs feed stocks are employed, to subject the feed stocks which are known to contain water and/or olens, such as butenes, pentenes, or lower molecular weight mnooletlns, to a pretreatment with a suitable agentior the removal of water and/or olefins if-they are titles.

or higher. or the -use of chlorsulfonic or :ducrsulfonic acid for the same purpose, or various other types of common expedients for removal treated through a suitable filter filled with a copresent in objectionable quanl Buch a treatment may embody the yuse of vconcentrated sulfuric acid gf the order of 98% agulating or adsorbing medium in order to condition the feed for its subsequent isomerization treatment.

In general, the process of the present invention resides in the pretreatment of olefin-containinghydrocarbon mixtures, which also contain substantial amounts of normal parai'ilns of at least four carbon atoms per molecule, with sulfuric acid of at least 80% concentration, at room temperature or in general between about 50 F. and about v150 F. to remove from the feed stock the oleilnic impurities contained therein. It has been discovered, however, that such a treatment alone is not sufficient to preserve the most efficient activity of the catalyst mass. Attempts have been made to remove the sulfur bodies which may have been present originally, that is, prior to the pretreatment with sulfuric acid, or which may have been introduced into the feed stock by reason of the sulfuric acid pretreatment, by means of a knockout drum or some other suitable device which depends upon gravity separation oi small amounts of residual sulfuric acid and other sulfur bodies contained in the isomerization feed gases. This has proved ineffective. It has been found that'the feed stock after passage through the sulfuric acid absorber and drier still contains small quantities of sulfur compounds which cannot be removed by a knockout drum or by nltration.

It has now been discovered further that in order to preserve the highest activity for the Friedel-Crafts type catalysts, say, for example, aluminum chlorideffor its use in the isomerizaor a mixture of two or more of the following materials: Activated Alumina, alumina gel, bauxite, Porocel, silica gel, diatcmaceous earth, kaolin, bentonite, kieselguhr, and so forth. It is preferred, however, to employ those materials comprising essentially alumina as their base, although the other adsorptives mentioned are also highly Auseful. Since the Friedel-Crafts type catalysts tially anhydrous condition, at least to the point tion of normal parafflns that a second and subsequent treatment of the feed gases is necessary. This pretreatment immediately follows the pretreatment with sulfuric acid as heretofore specified and consists in contacting the feed stock for the isomerization. reaction with a porous adsorbent which, it has been found, is very effective in the removal of the sulfur bodies from the feed stream. By the use of such a feed stock so pretreated, the catalyst life of the aluminum chloride, for example, has been greatly increased. Also, the yield of desired isoparaiiins has been increased as compared with the catalyst life and yield of isoparaflins obtained in cases where the pretreatment with adsorbent materials has been omitted. It is preferred that the sulfuric acid and adsorbent material treatments be carried out with the feed stock in the liquid phase, although improved results arevalso obtained where these pretreatments are carried out with the feed stock being in the vapor phase. The relative amounts of sulfuric acid and adsorbent material required depend to a large extent upon the amountof impurities to be removed and it is readily apparent to those familiar with absorption and adsorption operations the amounts of materials required to accomplish the desired impurity removal. As the sulfuric acid and adsorbent material become saturated with the products removed, fresh quantities*v of' acid and adsorbent materials should be added and the spent materials removed from the contacting chambers.

The adsorbent material employed may be one where no free water is given off under the adsorption conditions obtaining. The conditioning of the adsorptive materials for use in the second pretreating step is readily accomplished by simply heating the materials to a temperature of from about 500 F. or 600 F. up to 1100 F. or 1200 F. for a period of time ranging between about 1 hour and about 7 or 8 hours.' It will be understood, of course', that temperatures and times outside of these ranges are equally effective so long as the free water whichmay be given off during the pretreating steps is effectively removed prior to the use of these materials for the pretreatment of the feed stocks and so long as adsorptivity is not reduced by excessive heat treatment. When used in the specification and claims, the terms sulfur compounds and "sulfur bodies are intended to include elemental sulfur and the simple esters and salts of inorganic and organic compounds containing sulfur, as well as hydrogen sulfide, mercaptans, sulfldes and sulfonates..

The accompanying drawing represents in more or less diagrammatical sectional elevation e. flow plan depicting a suitable. installation of the two pretreatment steps when used in conjunction with a normal paramn isomerization reaction. Referring to the drawing. a feed stock such as, for example, normal butane, normal pentane or the higher homologues thereof, or hydrocarbon mixtures predominating in these compounds which contain small amounts of sulfur bodies, water and/or olefins as impurities therein, is introduced in the liquid phase, by-means of line 2, con-A trolled by valve 3, into absorber 4 which is substantially filled with sulfuric acid of atleast concentration, preferably -98% concentration. by means of line 1, controlled by valve 8. This operation is carried out at a temperature ranging between about 50 F. and about 150 F., preferably at room temperature, and absorber 4 normally is packed with Raschig rings, or other steps taken to improve the degree of contact of the liquids therein. If necessary, sufficient superatmospheric pressure may be maintained on 'not only absorber 4 but also throughout the system to maintain liquid phase operation where specified. Continued passage of the feed stock through the sulfuric acid in absorber l results finally in the saturation of the sulfuric acid, and spent acid may be withdrawn through line 5,

controlled by valve 8, and fresh acid introduced treating tower 22 I which is at least 'duced at a rate and in 'and liquid impurities fall to the bottom of knockout drinn It by gravity and are removed from the system by line Il, controlled by valve I2. The liquid freed of these-droplets iswithdrawn from knockout drum Il by means of line I4, controlled by valve I5, and maythen follow one or any combination or all of three possible paths, depending upon the quantity of impurities contained in the normalbutane liquid being subjected to the second treating operation. Thus, for example, the feed material may pass through line l5, controlled by valve Il, through line l5,

controlled by valve I5, or through line 20, controlled by valve 2l, or through all three lines o'r any combination of two of these lines, into 'the` which is substantially filled with a Porocel which is at least partially dehydrated, at least to is given oil.' under th'e adsorbent conditions maintained.- Means are provided (not shown) at the top and bottom of treating tower 22 for the introduction of fresh treating agent and for the removal of spent treating agent, respectively. A partially dehydrated bauxite such as Porocel is employed in the treating -tower 22and the liquid' feed is allowed to percolat'e downwardly therethrough, being then withdrawn from the bottom of tower 22 by means of.line 25, controlled by valve 25. 'Ireating tower 22 may also be arranged for upflow operation if desired.

The feed stock so purified, and from which the contaminants have been removed, is then sublected to an isomeriz'ation treatment which em-.

bodies the heating of the feed stock, that is, normal butane in the present instance, by means of heater 21 to the desired isomerization reaction temperature. A drawoil' line 25, provided with valve 29, is attached to the heating coil in heater 21 at an intermediate point so that only a partial heating is attained for that portion ot the feed stock so'withdrawn, whereas the fully heated feed stock is withdrawn through line 30,'controlled by valves 32 and 42. This partial heating of the feed stock is designed for the control of the temperature of the feed stock in line 3| just prior to enteringthe catalyst pickup chamber Il, partially illled with lumps or solid particles of aluminum chloride. The temperaturelof the hydrocarbon gases entering pickup chamber 33 through line Il and passing upwardly through this partially sublimes the aluminum chloride and carries the same, by means of line 3l, controlled by valve I9, and line 40, into the bottom of the isomerization reaction chamber 45 which contains; and is substantially iilled with, a suitable carrier such as Porocel having a water content ranging somewhere between about 0.5% and 2%. The aluminum chloride vapors are deposited on this Porocel and thereby form the catalyst bed. These vapors are also intromaintain the lactive aluminum chloride content of the catalyst bed in reactor 45 substantially constant, and this is accomplished by regulating the temperature of the normal butane vapors entering the bottom ofthe catalyst pickup chamber 33 through control of valves 2l and Il. Once 'the isomerization reaction is under way land-thecatalyst bed is formed, so that only a substantially constant'a'ctive aluminum chloride content Aneed be maintained,Y only a portion' of--the feed vaporsv need pass either continuously or intermittently through catalyst pickup zone I3 while the greater portion oi', these vapors by-pass cat,-

alyst pickup chamber 33 1and enter the reactor an amount sumcient to the extent that no free water 3 to'wer 45 by means of line 4I, controlled by valve 42, which Joins with line 40 at the bottom of the reactor tower 45. Hydrogen chloride promoter in th'e amount ranging between about 2% and about 22%, preferably between 'about 4% and about 12 weight percent, based on hydrocarbon charge to the reactor, is introduced into the system through line 50, controlled by valve 6|, passes by means of line 52, controlled by valve 63,

into admixture with the normal butane vapors in line 4I and enters the reaction zone through line 40. The temperature of the normal butane vapors passing from heater 21 through' line 30 is generally between about 250 F. and about 350 F., while the temperatureof the vapors passing from heater 21 through line 28 is Vgenerally between about 220 F. and about 300 F. I'he catalyst bed in reactor 45 is maintained with an aluminum chloride concentration ranging between about 8 and about 1liv weight percent, preferably between l2 and 14 weight percent, although good isomerization is accomplished if higher or lower quantities of aluminum chloride are employed inv the catalyst bed. Preferably, hydrogen chloride is not added to the reaction zone while the aluminum chloride vapors admixed with normal paraffin feed stock are being intermittently introduced into' the catalyst bed. V

The feed is passed through reactor 45 Aat a rate of throughput between about 0.5 and about 2 v./v./hr.,- although it is understood that throughput rates outside of this particular range may also'be maintained with only a slight decrease in the overall yield'of desired product. 'I'he vapors passing overhead through line 46 enter cooler 4l, where they are condensed to liquid, and by means oi line 45 are passed into accumulator drum` 49. Any small particles of solid materials such as solid heavy liquid sludge which' may have been entrained in the vapors in line 46 are settled and removed through line 50, controlled by valve 5l. If desired. vent pipe 4.3, providedwith valve 44, serves to permit the removal of small amounts of permanent gases formed in the process. The liquid product is then withdrawn through line 52, controlled by valve 53, and enters stripping tower 54 which is designed to remove as overhead through' line 55 substantially all of the hydrogen chloride from the reacted mixture.

ping tower 54 may be designed and operated to permit the removal of substantial quantities of a case. the molecular hydrogen likewise is with'- -55, controlled by .valve 51.

drawn overhead from stripping tower 54 through line 55. A portion or all of these overhead materials may be bled from the system through line Generally, however, the greater part, if not all, of .this overhead is returned to the reaction -zone in reactor 45 by means of line 55, valve 55, line Q52, valve 53, and lines 4l and 40.

by valve 5l. The bottoms from stripper 54 are by means of line I4 and open valve 85,

intofractionating tower 'where any residual The desired isobutane fraction is withdrawn through line 159, controlled by valve l0, and the -unreacted normal butane and heavy degradation aluminum chloride for v The strip- Hydrogen chloride is introduced into' the system as required. through line l0, controlled 'products of the reaction, if any, are withdrawn as bottoms from tower through line 1l. A portion or all of these products may be withdrawn from the system through line 12, controlled by valve 13. Generally, however, the greater portion of these bottoms consisting of normal butane are recycled to the reactor 45 by means of line 14, valve and line 40 after first fractionating them to recover normal butane for recycling. The heavy bottoms are withdrawn from the system.

It is not essential that the isomerization reaction itself be conducted in the vapor phase, although' that is a preferred embodiment of the isomerization process when the feed stock is butane. The above described illustration,with/reference to the isomerization process may be conducted in liquid phase and at much lower temperatures. The above description with reference to the isomerization reaction and the process employed for carrying out the same is given so that a complete description of the invention which resides in the pretreating operations is fully understood. [n general, the isomerization catalyst, feed stock and conditions are well known and in so far as the isomerzation itself is concerned do not form a part of the invention except in so far asit is employed in commotion with the pretreating steps previously described.

Example treating operation but very poor results were ob` tained, as would be expected by those familiar with the process, whereas in the second instance a pretreating operation with sulfuric acid alone, and then with sulfuric acid followed by Porocel, was carried out. The sulfur content of the feed stock was almost negligible as it was originally received. The reaction was carried out in a tower maintained at about 300 F., under a pressure of about 200 pounds per' square inch gauge. The refinery C4 cut was passed at the rate of about 1 liquid volume of feed per volume of catalyst per hour through the reactor which was about 1.5 inch'es in diameter by about d feet high. this reactor being filled with Porocel which had been previously heated to about 1000 F. for about 12 hours. All of' the aluminum chloride was added as a vapor in the normal butane feed stock. About 6 weight percent of hydrogen chloride based on the feed was separately added to the reaction and was mixed on entering the reactor. A drum of solid granular aluminum chloride was maintained at about th'e same temperature as that of the reactor and the normal butane gas served as a carrier for the sublimed aluminum chloride. Measured amounts of aluminum chloride were placed in this catalyst pickup chamber from time to time. In the pretreatment with sulfuric acid, the acid concentration was held at 90-98% and the temperature of the sulfuric acid was maintained at about room temperature. 'I'he Porocel, in the case where Porocel was employed following th'e sulfuric acid pretreatment, was also maintained at room temperature. An analysis of the feed stock coming from'the sulfuric acid pretreatment was made by conventional means. The reaction conditions were so adjusted as to j aeaesaf,

maintain a substantially constant conversion of about 40% of the vnormal bi1-tane to isobutane. The following data were obtained:

It win be noted that the aluminum chloridel Was about twice as effective for catalyzing the isomerization reaction where a Porocel treatment of the feed stockvfollowed the sulfuric acid treatment as in the case where a simple sulfuric acid treatment alone was employed.

Having thus fully described and illustrated the nature of the invention, what is desired to be secured by Letters Patent is:

1. In a process of isomerlzing straight chain parains of at least four carbon atoms per molecule in the presence of a Friedel-Crafts type c catalyst and a halogen-halidef promoter under isomerization reaction conditions to produce branched chain parafllns, wherein a feed stock containing' said straight chain parafilns is pretreated with a concentrated mineral sulfur-OXY- gen acid to remove impurities therefrom, the improvement comprising contacting the acidtreated feed stock with a porous alumina prior to isomerizing the said straight chain paran feed stock.

2. In a process of isomerlzing straight chain paraiiins of at least four carbon atoms per molecule in the presence of a Friedel-Crafts type catalyst and a halogen-halide promoter under isomerlzation reaction conditions to produce branched chain paraillns, wherein a feed stock containing said straight chain parafhns is pretreated with a concentrated mineral sulfur-oxygen acid to remove impurities therefrom, the improvement comprising contacting the acidtreated feed stock with at least a partially dehydrated bauxite prior to isomerizing the said straightvchfain parain feed stock.

3. In a process of isomerizing straight chain paralns of at least. four carbon atoms per molecule, in the vapor phase, in the presence of aluminum chloride on a partially dehydrated bauxite and in the presence of promotional amounts of hydrogen chloride, under isomerization reaction conditions, to produce the corresponding branched chain parafiins, the improvements comprising treating a feed stock containing said straight chain paralns with sulfuric acid of at least concentration followed by treating the feed stock with at least a partially dehydrated bauxite which has previously been heated to a suiciently high temperature to insure that substantially no free water will be given o under y conditions,

hydrogen chloride, under isomerization reaction corresponding to produce the branched chain parailn,d the improvements comprising treating a feed stock containing said straight chain paralns with sulfuric acid of at least 80% concentration followed by treating the feed stock with at least a, partially dehydrated bauxite which .has been previously heated to a 1 Asuiciently high temperature toinsure that substantially no free water will be given oi! under the conditions obtaining prior to isomerizing the straight chain paraffin feed stock, and wherein both pretreatments are carried out with the feed stock being. in the liquid phase.

5.1In a process of isomerizing straight chain parains of at least four carbon atoms per molecule, in the vapor phase, in the presence of aluminum chloride on a partially dehydrated bauxite and in the presence of promotional amounts of hydrogen chloride, under isomerization reaction conditions. to produce the branched chain paraffin, the improvements comprising treating a feed stock containing said straight chain parailins with sulfuric acid of between about 85% and about 100% concentration followed by treating the feed stock with at leasta partially dehydrated bauxite which has previously been heated to a sumciently high temperature f to insure that substantially no free water will be given oil under the conditions obtaining prior to isomerizing the straight chain paraiiln feed stock. i

6. A process as in claim 8 wherein the catalyst carrier and the material employed in the second pretreating Operation are substantially identical.

:,seaeas corresponding 7.'A process for' the isomerization of normal. paramns of at least four carbon atoms per molecule in the presence of aluminum chloride and hydrogen chloride under isomerization reaction conditions. the steps comprising pretreating a feed stock containing said normal paramns in the liquid phase lwith sulfuric acid of at least concentration' to remove impurities deleterious to the isomerizing activity of the aluminum chloride, followed -by liquid phase contacting of the feed stock so treated with at least a partially dehydrated bauxite incapable of giving olf free water under the conditions obtaining. thereby removing sulfur bodies from the feed stock and then subjecting the same to the isomerization reaction. i

8. A process as in claiml 7 wherein the feed 'stock is essentially normal butane but contains small amounts of oletlns as impurities therein.

l 9. A process as in claim 7 wherein the feed stock is essentially normal pentane but contains small amounts of oleins as impurities therein.

10. A process as in claim 7 wherein the bauxite pretreatment is carried out at a temperature of between about 50 F. and about 150 F.'

11. A process as in claim 'l wherein the bauxite pretreatment is carried out at a temperature of between about 50 l F. and about 150 F. and wherein the isomerization reaction is carried out at a temperature of between about 250 F. and about 350 F. in the vapor phase.

12. A process as in claim 'I wherein the bauxite pretreatment is carried out at a temperature of between about 50 F. and about 150 F., wherein the isomerization reaction is carried out at a temperature of between about 250 F. and about 350 F. in the vapor phase and wherein the sulfuric Y acid is of a concentration between about and about l NQRVAL F. Mms. 

